@johnpoz
I originally used fe80::/16, which you told me was incorrect (which is true... it should be fe80::/10 like you mentioned). But then you said this:
An alias for any specific "net" using the space of /16 wouldn't be a specific net, it would be a huge chuck of the whole space FE80::/10, where did you come up with using /16 anyway?
The way I interpreted that, was that using /10 also wasn't ideal, and using a /64 would use less space (and would be closer to a * net). Both /64 and /10 both work, so I can update the Redmine ticket if you think /10 should be the correct default.
224.0.0.0/3 is the multicast address space. Originally I created individual rules for each specific address, but decided to "simplify" doing that and instead creating an alias that included the entire multicast address space. My alias is called MULTICAST_SUBNET, and includes the network of 224.0.0.0/3 which is technically correct right? I use more then just mDNS requests fall into that subnet. But you are 100% correct that I should update that ticket and make it 224.0.0.251, since that is unique to mDNS and is the only destination required for Avahi.
Something else related to this thread... some of my devices on some VLANS make requests for SSDP. They have an IPv4 destination of 239.255.255.250. However, IPv6 traffic is blocked by default unless this rule is created:
source: fe80::/10
destination: ff02::c
Port: 1900
Another example would be the same source and destination above, but for port 3702 which is WSDD (used by a Windows 10 device).
These are examples of traffic where I would assume (incorrectly based on your feedback) the * net source rule to cover when IPv6 is enabled on on a network.
And no offense taken. I'm far from an expert here. I've already solved this myself, although you may see the way I've done it is less then ideal. I created this post to hopefully help others.